1. Field of the Invention
The present invention relates to a high power optical connector, and more particularly, to a high power optical connector suitable for connection of an optical fiber for high power transmission of several hundreds of mW to several tens of W. In addition, the present invention relates to an optical fiber system using the high power optical connector on a receiving side.
2. Description of the Related Art
Conventional arts in relation to the present invention are disclosed in, for examples, Patent Documents described as follows.
In Japanese Unexamined Patent Application, First Publication No. 2004-29450 (hereinafter, referred to as Patent Document 1) and Japanese Patent, Publication No. 3831315 (hereinafter, referred to as Patent Document 2), techniques for reducing power density by increasing mode field diameters are disclosed.
In Japanese Patent, Publication No. 2835384 (hereinafter, referred to as Patent Document 3), an optical fiber connector which detachably connects first and second optical fibers used for high-power laser beam and has temperature measuring device for measuring the temperature of a connection portion—Between the first and second optical fibers, is disclosed.
In Japanese Examined Utility Model Application, First Publication No. H03-17284 (hereinafter, referred to as Patent Document 4), an optical connector in which a space is provided in the vicinity of fiber end faces to thereby prevent being heated and damaged even if portions other than the end faces are irradiated, is disclosed.
In general, for an optical connector, a zirconia ferrule is used. Since zirconia absorbs light leakage, the temperature of the ferrule portion increases, and the temperature of an adhesive for fixing a fiber inside a fine hole also increases. As a result, there is a concern that changes in characteristics such as degradation of adhesion and an increase in absorptance occur.
In addition, when the ferrule portion is inserted into a general optical connector, a sleeve expands. Therefore, the sleeve and a housing are designed to have a slight gap. Accordingly, light leakage is absorbed by the zirconia ferrule which results in storing heat. As a result, when high power light leaks, the temperature of the ferrule portion rapidly increases, and the adhesive and the like may be damaged.
In the optical connector structure disclosed in Patent Document 3, light leakage is absorbed by a portion with the highest power density in the vicinity of a connection point. In this structure, when the temperature increase is detected, there is a high possibility in that the end face is already damaged. Therefore, reliability is low.
In addition, in this conventional technique, the temperature is monitored at a position apart from the point absorbing light. Therefore, a difference between the temperatures of the practical ferrule and the monitor occurs, or a time lag (time interval) at the time of monitoring occurs. This results in low reliability.
It is thought that the optical connector structure disclosed in Patent Document 1 is effective when light of about 1 W is transmitted by using a single-mode fiber for communications. However, in the case of a high power light transmission of about 10 W which is the target of the present invention, temperature increase in a position irradiated by light leakage is high even though a mode field diameter is increased, and this may damage the structure.
In the optical connector structure disclosed in Patent Document 4, light is focused on a lens to enter the optical connector. However, in this structure, a connection loss is greater than that of a PC (physical contact) connection. Accordingly, power of incident light needs to be increased, or the number of LDs (laser diodes) needs to be increased. This results in increases in power consumption and costs.
The present invention was made in view of the above-mentioned circumstances and has an object of providing a high power optical connector which will not be damaged during connection between optical fibers for high power light transmission and guarantees a long life-span, and an optical fiber system using the same.